Dichlorodistannoxane transesterification catalysts, pure Lewis acids.

Dialkoxy- or diacyloxy-distannoxanes were transformed into unsymmetrical acyloxyalkoxydistannoxanes during a transesterification reaction where they were used as catalysts, while more active dichlorodistannoxanes were recovered unchanged.

Dichlorobis(pyridine-kappa N)bis(3,3,3-trifluoropropyl-kappa C(1))tin(IV).

In the title compound, [Sn(C(3)H(4)F(3))(2)Cl(2)(C(5)H(5)N)(2)], the Sn atom lies on an inversion centre and is octahedrally coordinated by two Cl atoms, two trifluoropropyl groups and two N atoms in an all-trans configuration. The electronegative trifluoropropyl groups increase the electrophilic properties of the Sn atom, and the Sn[bond]Cl and Sn[bond]N bonds are shortened in comparison with those reported for analogous compounds.

Finite time blow-up in some models of chemotaxis.

We consider a class of models of chemotactic bacterial populations, introduced by Keller-Segel. For those models, we investigate the possibility of chemotactic collapse, in other words, the possibility that in finite time the population of predators aggregates to form a delta-function. To study this phenomenon, we construct self-similar solutions, which may or may not blow-up (in finite time), depending on the relative strength of three mechanisms in competition: (i) the chemotactic attraction of bacteria towards regions of high concentration in substrate (ii) the rate of consumption of the substrate by the bacteria and (iii) (possibly) the diffusion of bacteria.

Long-chain-substituted uric acid and 5,6-diaminouracil derivatives as novel agents against free radical processes: synthesis and in vitro activity.

A new series of N-alkylated uric acids (2,6,8-purinetrione) and 5,6-diaminouracils (5,6-diamino-2,4-pyrimidinedione) were synthesized, and their activities against free radicals were evaluated. Long-chain derivatives of both series exhibited a large inhibitory activity against oxygen radical induced lipid peroxidation in bovine heart mitochondria (IC50 lower than 1 microM), compared to the reference antioxidants trolox C or alpha-tocopherol. This activity appeared related to (i) the ability of these compounds to reduce the stable radical 1,1-diphenyl-2-picrylhydrazyl and (ii) their lipophilicity estimated by log P determination.